On typical rear-wheel drive vehicles, the engine and transmission are mounted on the vehicle frame, and the driving wheels are free to move up and down in relation to the frame. This design causes constant changes in the angularity of the driveline during vehicle operation. Therefore, constant velocity universal joints are used to provide the necessary flexibility in the driveline or drive train to accommodate these changes in angularity. Universal joints are typically employed at the front and rear of the propeller shaft. The front universal joint is connected to the gearbox output shaft by a coupling. The rear universal joint is connected by a yoke to the differential drive pinion gear shaft. This balanced arrangement of power transfer components serves to compensate for any changes in the driveline. Vehicles having two propeller shafts also have a third universal joint provided therebetween.
The propeller shaft on rear-wheel drive vehicles may be formed of solid tubular steel having a one-piece construction. On typical front-engine rear wheel drive vehicles, the propeller shaft transmits the driving effort from the mainshaft of the gearbox to the final drive. The final drive, in turn, is mounted either to a sprung rear axle or, in the case of vehicles having independently sprung and driven rear wheels, to a separate housing attached to the vehicle structure. In light, medium, and heavy-duty vehicles with front engines, a transmission gearbox is separated from the final drive by the propeller shaft. The driveline connects the transmission with the rear driving axles and effectively transmits engine power to the driving wheels.
One type of universal joint commonly used in today's automobiles is a plunging type constant velocity universal joint of the tripod or ball and cage variety. Tripod-type constant velocity universal joints are characterized by an outer joint disposed around an inner joint which has a plurality of arms projecting therefrom which travel in the grooves of the outer joint. The plunging ball and cage joint type resembles the classic Rzeppa design but with plunging or end motion character. Plunging constant velocity universal joints allow the shaft which interconnects with the universal joint to change length during operation without the use of splines. Plunging joints are widely used on the inboard (transmission side) joint of front-wheel drive vehicles.
The transmission gearbox has a mainshaft or output shaft which has attached to it a gearbox flanged coupling which is coupled to a propeller shaft in order to transmit torque to the propeller shaft. As stated, a constant velocity universal joint is provided between the gearbox and the propeller shaft, and is coupled to the gearbox flanged coupling, in order to provide for angular deviation therebetween. The flange of both the gearbox flanged coupling and the flange of the mating universal joint each has typically six holes in respective alignment with each other, allowing them to be coupled via corresponding press-fit bolts and lugnuts.
This method of coupling the gearbox to the universal joint of the propeller shaft, however, is costly in terms of time, labor and piece price. It requires alignment between the corresponding holes and time involved in securing the six sets of bolts and nuts. Further, should the gearbox or constant velocity joint require maintenance, repair or replacement, any disassembly of the components may also prove to be time consuming. For example, it may be the case where the nuts and bolts become inseparable, thereby requiring a great amount of time and effort in separating the mating flanges. Vibration of the driveline may also be a concern after disconnection and subsequent reconnection of the propeller shaft from the gearbox. Because it is desired to preserve as much as possible the original state of balance, any loss of clamping load and separation at the mating faces of the coupled flanges may in some instances possibly introduce vibration into the driveline.
Under the current arrangement, the friction forces acting between the mating faces of the coupled flanges are being fully exploited to transmit the torque from the gearbox to the propeller shaft. The externally applied load acts in a plane perpendicular to the bolt axis and is transmitted by the frictional forces acting between the contacting faces of the constant velocity joint and the gearbox, which are tightly clamped together by these press-fit bolts and lugnuts.
Consequently, there is a need to improve the connection between the constant velocity joint of the propeller shaft to the adjoining gearbox or similar component, as well as a need for an assembly including a propeller shaft, constant velocity joint and gearbox which allows for a less costly assembly in terms of time, labor and part price, as well as allowing for less costly and less difficult maintenance and repair of the mating components. The improved connection and assembly should also allow for less noise, vibration and harshness, and should also provide for a better and more efficient torque transmittal between the mating components.